1. Field of the Invention
The present invention relates to a titanium nitride aluminum based sintered material effectively utilizable as the material of a tool for high speed cutting spheroidal graphite cast iron, etc., and a production method of this titanium nitride aluminum based sintered material.
2. Description of the Related Arts
The spheroidal graphite cast iron is cast iron in which spheroidal graphite is crystallized by adding cerium (Ce) or magnesium (Mg) (or a Mg alloy) into a molten bath of low sulfur (S) (&lt;0.02%) and low phosphorus (P) (&lt;0.2%). The spheroidal graphite cast iron has high tensile strength and relatively large tenacity in comparison with common cast iron. Therefore, the spheroidal graphite cast iron is widely used as a material of mechanical parts requiring strength and is also used in many cases as trunk important parts mainly constituting an automobile by its recent higher performance.
Cutting work of the spheroidal graphite cast iron is normally required after casting to set this spheroidal graphite cast iron to have a final shape size of the above trunk important parts, etc. A cutting work tool of the spheroidal graphite cast iron must have performance capable of rapidly processing this spheroidal graphite cast iron without any waste with required processing accuracy. When a tool edge is worn and damaged by chipping, etc., fins are caused on a processing surface of the spheroidal graphite cast iron, etc. so that no required size accuracy and surface roughness are obtained. Accordingly, a defective product is formed so that this defective product cannot be forwarded as manufactured goods.
Therefore, when the above tool wearing and chipping damage, etc. are caused, the cutting work tool must be immediately exchanged. This tool exchange must be reduced as much as possible since this tool exchange causes a reduction in productivity. Further, when production cost of the above cutting work tool is high even if life of this tool can be lengthened, processing cost of the cutting work tool rises as a result.
Accordingly, a cutting work tool having a long life and cheaply manufactured without any wearing nor damages of the above tool edge by chipping, etc., is strongly desired to cut the spheroidal graphite cast iron at high speed with reduced processing cost mentioned above.
For example, a ceramic sintered body constructed by TiC, Al.sub.2 O.sub.3 and SiC whiskers as described in Japanese Published Patent No. 8-16028 is proposed as a cutting work tool for solving the above disadvantages.
However, there are the following problems with respect to a sintered material used in the above conventional cutting tool, etc.
Namely, no expensive cubic boron nitride as a high hardness material is included in the ceramic sintered body constructed by the above TiC, Al.sub.2 O.sub.3 and SiC whiskers. Therefore, there is a merit in that the ceramic sintered body can be cheaply manufactured. However, no ceramic sintered body can have durability for realizing a long life at a desired level. In particular, no satisfied durability can yet be obtained with respect to the spheroidal graphite cast iron including magnesium (Mg) and difficult to be processed.